Index: Ringtoets/Integration/src/Ringtoets.Integration.Forms/PropertyClasses/FailureMechanismContributionProperties.cs
===================================================================
diff -u -rb2b9fdf365e70928a05c57966eeed30d9050e528 -r58e63d129c58c0247ce8918486f4e68120876bd9
--- Ringtoets/Integration/src/Ringtoets.Integration.Forms/PropertyClasses/FailureMechanismContributionProperties.cs	(.../FailureMechanismContributionProperties.cs)	(revision b2b9fdf365e70928a05c57966eeed30d9050e528)
+++ Ringtoets/Integration/src/Ringtoets.Integration.Forms/PropertyClasses/FailureMechanismContributionProperties.cs	(.../FailureMechanismContributionProperties.cs)	(revision 58e63d129c58c0247ce8918486f4e68120876bd9)
@@ -23,7 +23,6 @@
 using System.Collections.Generic;
 using System.ComponentModel;
 using Core.Common.Base;
-using Core.Common.Gui.Attributes;
 using Core.Common.Gui.PropertyBag;
 using Core.Common.Utils;
 using Core.Common.Utils.Attributes;
@@ -39,9 +38,9 @@
     /// </summary>
     public class FailureMechanismContributionProperties : ObjectProperties<FailureMechanismContribution>
     {
-        private IFailureMechanismContributionNormChangeHandler normChangeHandler;
-        private IAssessmentSectionCompositionChangeHandler compositionChangeHandler;
-        private IAssessmentSection assessmentSection;
+        private readonly IFailureMechanismContributionNormChangeHandler normChangeHandler;
+        private readonly IAssessmentSectionCompositionChangeHandler compositionChangeHandler;
+        private readonly IAssessmentSection assessmentSection;
 
         /// <summary>
         /// Creates a new instance of <see cref="FailureMechanismContributionProperties"/>.